The present invention relates to polishing pads for chemical mechanical polishing of substrates, and in particular, relates to resilient, laminated polishing pads and methods therefor.
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a semiconductor wafer. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modem processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and electrochemical plating (ECP).
As layers of materials are sequentially deposited and removed, the uppermost surface of the wafer becomes non-planar. Because subsequent semiconductor processing (e.g., metallization) requires the wafer to have a flat surface, the wafer needs to be planarized. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damages, scratches, and contaminated layers or materials.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is a common technique used to planarize substrates such as semiconductor wafers. In conventional CMP, a wafer is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the wafer, pressing it against the polishing pad. The pad is optionally moved (e.g., rotated) relative to the wafer by an external driving force. Simultaneously therewith, a chemical composition or other fluid medium (“slurry”) is flowed onto the polishing pad and into the gap between the wafer and the polishing pad. The wafer surface is thus polished and made planar by the chemical and mechanical action of the pad surface and slurry.
Rutherford et al., in U.S. Pat. No. 6,007,407, discloses polishing pads for performing CMP that are formed by laminating two layers of different materials. The typical two-layer polishing pad includes an upper polishing layer formed of a material, such as, polyurethane suitable for polishing the surface of a substrate in the presence of a polishing solution (e.g., slurry). The upper polishing layer is attached to a lower layer or “sub-pad” formed from a material suitable for supporting the polishing layer. The sub-pad typically has higher compressibility and lower stiffness than the polishing layer and essentially acts as supporting “cushions” for the polishing layer. Conventionally, the two layers are bonded with a pressure-sensitive adhesive (“PSA”). However, PSAs have relatively low bonding strength and marginal chemical resistance. Consequently, a laminated polishing pad utilizing PSAs tend to cause the sub-pad to separate (“delaminate”) from the upper polishing layer, or vice versa, during polishing, rendering the pad useless and impeding the polishing process.
Also, certain polishing pads for performing CMP have windows formed therein. These windows allow light from an in-situ end point detection measurement system to reach the wafer being polished to monitor the polishing process. Pad windows need to be strongly bonded to the pads, otherwise they can also separate from the sub-pad and/or polishing layer and become damaged, rendering the pad and the window useless.
Therefore, what is needed is a polishing pad for chemical mechanical polishing, including polishing pads with windows, which resists delamination and are cost effective to manufacture.